Engineered miniature CRISPR-Cas system for mammalian genome regulation and editing

September, 2021

In brief:

Xu et. al developed a miniature CRISPR system for genome engineering via protein and guide RNA engineering. Whereas the natural Cas12f does not function in mammalian cells, engineered Cas12f mutants, named CasMINI, show comparable activities with Cas12a for efficient gene activation. CasMINI also enables robust gene editing and base editing.

Highlights

• Protein and RNA engineering enable Cas12f to function robustly in mammalian cells
• The engineered CasMINI is compact and less than half the size of Cas9 and Cas12a
• CasMINI is efficient and specific for gene activation and is comparable with Cas12a
• CasMINI is versatile and allows robust genome editing and base editing

Summary

Compact and versatile CRISPR-Cas systems will enable genome engineering applications through high-efficiency delivery in a wide variety of contexts. Here, we create an efficient miniature Cas system (CasMINI) engineered from the type V-F Cas12f (Cas14) system by guide RNA and protein engineering, which is less than half the size of currently used CRISPR systems (Cas9 or Cas12a). We demonstrate that CasMINI can drive high levels of gene activation (up to thousands-fold increases), while the natural Cas12f system fails to function in mammalian cells. We show that the CasMINI system has comparable activities to Cas12a for gene activation, is highly specific, and allows robust base editing and gene editing. We expect that CasMINI can be broadly useful for cell engineering and gene therapy applications ex vivo and in vivo.